Eventually, stand-alone PCs evolved into PC networks, most often comprising a central network server from which client PCs branch. The network server is a focal point for processing and storage in the network, as the network server is responsible for distribution of application programs and data to the client PCs. Since they must serve as a focal point, network servers are typically outfitted with the latest, fastest, largest central processing unit ("CPU"), buses and random access memory ("RAM"). Further, such network servers are provided with at least one (and almost always more than one) large, fast hard disk drive providing nonvolatile storage for the application programs and data.
Network servers often employ more than one disk drive for three reasons. First, storage needs may exceed the capacity of today's largest single drives. Second, large drives are often more expensive per unit of storage than smaller drives. Third, it is advantageous from the standpoint of reliability to spread the application programs and data over multiple disks such that, if one disk fails, all is not lost. In fact, it has been recognized that an array of relatively inexpensive disks may act in concert to provide nonvolatile storage that is faster and more reliable than a single large expensive disk drive.
The technology to enable such inexpensive disks to cooperate advantageously is generally known as Redundant Array of Inexpensive Disks ("RAID") and is particularly useful in the environment of network servers. RAID provides data redundancy, such that if a single disk drive fails, the data stored thereon can be reconstructed from the data stored on the remaining disks. There are several levels of RAID, depending upon the degree of speed and reliability desired. The reader is directed to widely-available publications on RAID and the advantages thereof, as a general description of RAID is outside the scope of the present discussion.
In the most sophisticated network servers, a failed disk drive can be replaced and the data thereon restored by software without interrupting the server's operation. In so-called "hot plugging", the failed disk drive is removed and a new one installed in its place without cutting off the power to the drive.
Given the above, it is apparent that a network server is advantageously housed in a main chassis, or "frame", most often in the form of a tower, containing multiple bays for receiving the various hard disk drives that comprise the network server's nonvolatile storage. It is desirable to provide a rapid, convenient means of installing disk drives in, and removing disk drives from, the bays. It is especially desirable in the context of RAID, wherein a drive may be hot-plugged into the bay.
There are five attributes that a well-designed structure for removably mounting a disk drive chassis within a bay. First, the structure should provide mechanical advantage for ease of insertion and removal of the chassis. This reduces the force a user is required to exert to install or remove the chassis. Second, the structure should provide self-alignment for a carrier that cradles the chassis. Self-alignment ensures proper position and orientation for the chassis carrier and any movable parts associated with the chassis carrier (such as the mechanism affording mechanical advantage). Third, the structure should provide positive latching for retaining the chassis in place once installed. Fourth, the structure should provide a handle for carrying the disk drive when it is removed. Finally, the structure should be cost- and space-efficient.
There have been attempts in the past to provide removable installation of a disk drive chassis in a bay. In one system, a lever and cam mechanism is provided to give mechanical advantage to urge the drive into place, but the lever and gearing mechanism is located under the drive, limiting the number of drives that can be located in a vertical array of bays of a given height. The location of the lever and gearing mechanism further restricts air flow between the installed disk drives. Finally, the lever cannot be used as a handle once the disk drive is removed.
In another system, a handle and cam mechanism cooperate to give mechanical advantage to the user, but the handle must be aligned manually before the carrier can be fully inserted into the bay; there is no automatic alignment.
In yet another system, separate lever and cam mechanisms are located on either side of the disk drive carrier. However, the levers must be separately aligned manually before the carrier can be fully inserted into the bay; again, there is no automatic alignment. Further, the levers do not function well as a handle.
In still another system, a handle and slot/pin mechanism provides the necessary mechanical advantage for insertion and removal. However, there is no positive latching for retaining the chassis in place once installed. Thus, the chassis is free to separate from the frame once installed.
Accordingly, what is needed in the art is a structure for removably mounting a computer peripheral chassis within a bay in a frame that provides a handle for the disk drive, alignment of the chassis carrier, mechanical advantage for ease of insertion and removal of the chassis and positive latching for retaining the chassis in place.